Dimensional weight: why a smaller box saves you money
3 min read
How carriers bill by dimensional weight, the DIM formula, and why right-sizing your box lowers shipping cost.
Carriers bill by size, not just weight
Major carriers charge by whichever is greater: the actual weight, or the dimensional (volumetric) weight of the box. A big, light box can cost as much to ship as a small, heavy one. That's why an oversized box quietly inflates every shipment.
The DIM weight formula
Dimensional weight is the box volume divided by a carrier divisor. For domestic retail rates the divisor is commonly 139: multiply length × width × height in inches, divide by 139, and round up to get the dim weight in pounds. A 12×12×12 box, for example, works out to about 13 lb of dimensional weight before you've put anything in it.
Right-sizing pays off on every order
Choosing the tightest box that safely fits your product, with just enough padding, lowers the dimensional weight and the postage on every single shipment. Across hundreds of orders that adds up fast.
See the dim weight before you buy
Find My Box shows the estimated dimensional weight for every matching box, so you can pick the size that protects your product and your shipping budget at the same time.
Find the right box in seconds
Enter your item and we'll return the tightest box that fits, with the price and shipping weight.
FAQ
How is dimensional weight calculated?
Multiply the box length × width × height in inches, divide by the carrier divisor (commonly 139 for domestic retail), and round up. The result is the dim weight in pounds.
Why does a bigger box cost more to ship even if it's light?
Because carriers bill on the greater of actual weight or dimensional weight. A large, light box has a high dimensional weight, so it's billed as if it were heavier.
How do I lower my shipping cost?
Right-size the box to the contents with just enough padding. A tighter box has a lower dimensional weight, which lowers postage on every order.